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Monthly Archives for June 2018

I’ll be taking a week off from the Blog (at this stage – may be longer) due to a resurgent CFS (Chronic Fatigue Syndrome). I have been battling this ‘outbreak’ for about 6 weeks and there has been very little improvement, so I need to take some ‘health time.’ Back when I can be.

The key to a stick insect’s survival may be allowing their eggs to be eaten and excreted by birds, according to new Japanese research.

Phasmatodea – more commonly known as stick insects – were so named because they genuinely look just like sticks.

While some stick insects do look like the classic stick – mottled brown with elongated limbs – others look remarkably like green leaves. They even have intricate leaf-like veins in their broad green wings.

Stick insects use camouflage to hide from predators.Shutterstock

But these new findings show that not only do these insects look like plants, they also behave like them – by using birds to disperse their offspring.

They fed three eggs from three stick insect species to their main bird predator, the brown-eared bulbul. Within three hours, 5-20% of these eggs had been defecated and were completely intact.

Even more impressively, a few of these eggs subsequently hatched. This leads us to ask what would happen if an adult female was eaten by a bird. Would the eggs inside of unlucky stick insect survive the bird’s digestive system and stand a chance of making it out at the other end?

Creative transportation

Plants have evolved ingenious ways of moving their seeds across large distances. Some seeds are carried by the wind or ocean currents, or by animals. Bushwalkers will be very familiar with prickly seeds designed to attach to animal hair, as they are also annoyingly good at sticking to trousers.

Prickly stick insect.Shutterstock

Many plants pack their seeds in delicious fruit which attracts animals with bright colours and alluring fragrances. When animals eat the fruit, some of the seeds make it through their digestive tract and are deposited far away.

This gives these seeds a better chance at survival, because they are not in competition with the parent plant.

This is a challenge that stick insects also face, as they’re not the most mobile twigs on the bush. Stick insects are slow and only move at night to avoid being seen by predators. Dispersal by birds helps avoid localised competition between generations.

Everyone wins

Stick insects and plants have also developed a mutually beneficial relationship with ants to disperse their eggs and seeds.

In Australia, we have a huge diversity of “myrmecochorous” plants (trees and shrubs whose seeds are picked up and carried by ants). These plants attract ants with “elaiosomes”, which are small structures on their outer surface packed full of nutritious ant food.

Some species stick insects’ eggs also have strange-looking structures on their outer surface. It turns out that these structures, called “capitula”, are also full of nutritious ant food. And sure enough, after the eggs are laid, ants will pick them up and carry them to their nests.

Covering roofs and walls of buildings with vegetation is a good way of reducing greenhouse gas emissions. And these green roofs and walls make cities look nicer. Toronto’s central business district adopted a policy of establishing green roofs on around half of all city buildings in 2009. Research shows this could reduce maximum city temperatures by up to 5℃.

We spent the past 12 months analysing the case for more greenery on Australian city buildings, drawing on international comparisons. We’ve shown that a mandatory policy, coupled with incentives to encourage new and retrofitted green roofs and walls, will provide environmental, social and business benefits.

These include improved air quality, energy conservation and reductions in stormwater run-off from buildings, which would decrease flash flooding. Green roofs and walls also become new habitats for biodiversity and can be pleasant spaces for social interaction in dense urban areas.

We found numerous studies confirming that greenery on inner-city buildings reduces the urban heat island effect, which is when city centres are hotter than surrounding suburban and outer-urban areas.

Green roofs are great social spaces.Author provided, Author provided

What other countries are doing

We examined international case studies of cities embracing green roofs and walls to review policy frameworks which could be suitable for Australia. A range of measures and policies exist and vary depending on building types (buildings need specific features to host vegetation) and the degree to which policies can be enforced.

Singapore is leading in this area. It markets itself as a “garden city” to attract investment, visitors and commerce. Green roofs and walls are a vital and visual manifestation of this policy.

Green walls are aesthetically pleasing.Author provided

Greenery is ingrained in Singapore’s development sector and is boosted by incentives, grants, awards, certification schemes and government-led development. Through this voluntary-heavy (yet supported) effort, Singapore increased its number of green roofs and spaces nine-fold between 2006 and 2016.

Rotterdam’s efforts weren’t as extensive as Singapore’s, but the city more than doubled its green roof area from 2012-2017 through incentives, grants, tax benefits and demonstration projects.

London increased its total green-roof area more than four-fold from 2005-2016. This was partially achieved through a biodiversity action plan.

And Toronto has the second-largest area of green roofs of the four cities we studied. This has been delivered through a mandatory policy, introduced in 2009, that requires all new developments with roofs of 2,000m² or more to install green roofs.

The case in Australia

We modelled what could be delivered in the City of Sydney and the City of Melbourne based on the measures taken in Singapore (which is voluntary-heavy), London (voluntary-light), Rotterdam (voluntary-medium) and Toronto (mandatory).

We combined this with data on actual green building projects in 2017 in Sydney and Melbourne to show the potential increase of projects in each city based on the four policies.

In the Sydney local government area, 123 green roof and wall projects were under way in 2016. The below table uses this base to estimate what the numbers of such projects would be for three time periods, based on the policies in the four scenarios modelled.

These policies appear most aligned with the voluntary-light approach adopted in London. Sydney had a 23% increase in green roofs since its policy launch, although this was from a very low starting point. Melbourne also reports an increase in green roofs and walls, though the amount of uptake isn’t publicly available.

There are, of course, barriers to greening up buildings. These include costs as well as lack of experience in the industry, especially in terms of construction and management. Professional capacity for green roofs is still in a developing phase and further training and skill development are needed.

Green wall adds vegetation to an aged care home in Sydney.

Around 87% of the building stock Australia will have in 2050 is already here, and a large proportion of existing buildings could be retrofitted. We recommend a voluntary approach using a mix of initiatives for building owners, such as tax benefits and credits in green building tools.

Focusing on new buildings is likely to lead to more modest growth rates in the short to medium term, relative to alternative approaches such as retrofitting. The annual growth rate of new stock is around 1-3%, which means that policies focusing on new stock will have a substantial impact over the long term.

However, in the short to medium term, a retrofit policy would have greater impact given the numbers of existing buildings suitable for this.

Local government areas can also promote the evidence showing the lift in property values in areas with more green infrastructure – in some instances up to 15%. This should encourage voluntary uptake.

The Australian Bureau of Statistics released the Australian Environmental-Economic Accounts on June 15. It’s a fine achievement, which shows, among other things, growing efficiency in water and energy use. That’s good for both the economy and the environment. Less good is that waste generation is increasing, broadly in line with GDP growth, as shown below.

Four reasons we neglect environmental accounts

So why no reaction to the environmental accounts? There are at least four reasons for this.

Firstly, few people in government or business are aware of the environmental accounts. While this was the fifth time the ABS has released the environmental accounts, and individual accounts for water and energy have a longer history, they remain little known.

The second reason is that it is not clear to government or business how the accounts should be interpreted. The ABS commentary is baldly descriptive:

More recently, between 2014-15 and 2015-16, the economy grew by 3%. At the same time, the population increased 2%; greenhouse gas emissions were up just under 1%; and Australian energy consumption increased less than 1%. Water consumption decreased 7% between these years. If the economy is growing at a faster rate than the consumption of our resources (or generation of waste and emissions), it is an indication that we are using our resources more efficiently, as measured by the Gross Value Added (GVA) of economic production per unit of resource use (or waste generated).

This is all true, but what does the information mean for the management of the economy and the environment? Of course, it is good that efficiency in resource use is improving. But we also need to understand what the limits are so that we can answer the key question: how much can we extract without risking the performance of the economy or the functioning of the environment?

For this we need other information. For example, to determine how much water we can use without damaging the environment we need information on the amount of water and the condition of ecosystems that depend on water in different places and times. With this information managers could compare the environment stress against the economic benefits or risks. All this can be done in an accounting framework, but is yet to occur.

It is also interesting that the ABS commentary neglects to mention waste. The amount of waste we produce is growing at about the same rate as GDP. Full waste accounts would improve our understanding of the reasons for this and the options for policy intervention. Sadly, while full waste accounts were prepared for 2010-11, they have not continued.

The partial picture means the interactions between the different parts of the environmental and the economy cannot be fully understood or explored. A key feature of the national accounts is that these are comprehensive. All industries and sectors of the economy are covered, with data on income, expenditure and assets.

In contrast, the national accounts are used, for example, by the Department of Finance for forecasting revenue, by Treasury for preparing the budget and economic policy, and by the Reserve Bank of Australia when setting interest rates.

The interest in the national accounts is also due to the understanding by business and the public that the health of the economy is directly linked to their own interests – i.e. profits for business and employment and income for people.

It’s also widely recognised that national accounts, and GDP in particular, are a good indicator of economic health. There is no similar indicator for the environment.

What can be done about this?

At present there is little understanding of how the environment contributes to the economy. Government agencies do not have regular information to assess the health of the environment, the adequacy of policies to stop environmental decline, or the economic impacts of environmental degradation.

How the strategy is implemented, however, will depend heavily on resourcing. This resourcing will need to consider not just the technical aspects of the accounts and related data sources but also the more challenging issue of how information from the accounts can be used in policy. Natural Capital Accounting for the Sustainable Development Goals recently summarised emerging examples from around the world.

Australia could establish a similar body to help develop a comprehensive set of environment accounts that meet policy needs. This would put us on the path to better policy, planning and management of both the economy and environment.

We would also get greater public discussion of the environmental accounts. Over time this might even rival the interest in the national accounts and GDP.

We collated information from about 100 previous local studies of cats’ diets across Australia. These studies involved teasing apart the contents of more than 10,000 samples of faeces or stomachs from cats collected as part of management programs.

We calculate that an average feral cat kills 225 reptiles per year, so the total feral cat population kills 596 million reptiles per year. This tally will vary significantly from year to year, because the cat population in inland Australia fluctuates widely between drought and rainy years.

On the hunt.NT government, Author provided

We also estimated that the average pet cat kills 14 reptiles per year. That means that Australia’s 3.9 million pet cats kill 53 million reptiles in total each year. However, there is much less firm evidence to quantify the impact of pet cats, mainly because it is much more straightforward to catch and autopsy feral cats to see what they have been eating, compared with pet cats.

Binge eaters

According to our study, cats have been known to kill 258 different Australian reptiles (snakes, lizards and turtles – but not crocodiles!), including 11 threatened species.

The cat autopsies revealed that some cats binge on reptiles, with many cases of individual cats having killed and consumed more than 20 individual lizards within the previous 24 hours. One cat’s stomach was found to contain no less than 40 lizards.

Such intensive predation probably puts severe pressure on local populations of some reptile species. There is now substantial evidence that cats are a primary cause of the ongoing decline of some threatened Australian reptile species, such as the Great Desert Skink.

By our estimate, the average Australian feral cat kills four times more lizards than the average free-roaming cat in the United States (which kills 59 individuals per year). But there are many more such cats in the US (between 30 million and 80 million), so the total toll on reptiles is likely similar.

The conservation of the Australian reptile fauna has been accorded lower public profile than that of many other groups. However, a recent international program has nearly completed an assessment of the conservation status of every one of Australia’s roughly 1,000 lizard and snake species.

Our research provides yet more evidence of the harm that cats are wreaking on Australia’s native wildlife. It underlines the need for more effective and strategic control of Australia’s feral cats, and for more responsible ownership of pet cats.

Pet cats that are allowed to roam will kill reptiles, birds and other small animals. Preventing pet cats from roaming will help the cats live longer and healthier lives – not to mention saving the lives of wildlife.

The authors acknowledge the contribution of Russell Palmer, Glenn Edwards, Alex Nankivell, John Read and Dani Stokeld to this research.